This invention relates generally to releasable fasteners of the type intended to secure two pieces of equipment or structural members together. More particularly, the present invention involves improvements in the fastener constructions illustrated and described in U.S. Pat. Nos. 3,309,115; 3,484,832; 3,528,690 and 3,712,653.
The devices shown in all of the above patents incorporate spring-type hook members which are associated with eccentric bushings of one form or another, such that when the bushing is turned, the spring on one panel or member is carried toward a fixed abutment or pin on the other of the members, and thereafter shifted laterally of the abutment so as to draw it inwardly toward the axis of the bushing, thereby locking the members together.
U.S. Pat. No. 3,528,690 involves a single S-shaped hook which accomplishes the desired locking. The remaining three patents identified above disclose devices employing not only simple S-shaped hooks but also more complicated arrangements and configurations entailing double hooks of relatively complex shape, these being bent from a single piece of wire stock. An example of such a complex hook is illustrated in FIG. 9 of U.S. Pat. No. 3,712,653. In addition, FIGS. 1 and 2 of U.S. Pat. No. 3,309,115 illustrate a different configuration of spring hook. Finally, FIGS. 10 and 11 of U.S. Pat. No. 3,484,832 show a still different design for a one-piece spring hook.
While the various arrangements disclosed in the above patents functioned in an acceptable manner for some purposes, several disadvantages become apparent. Where a single S-shaped hook was employed, the mechanism lacked strength and rigidity for all applications. That is, a single hook of relatively small gauge wire was in some cases not sufficiently stiff. Attempts to overcome this problem by employing a larger gauge wire resulted in increased cost, and more difficulty in bending and forming the wire to the desired shape, particularly where the wire was of spring-type stock.
In construction employing a double spring that was constituted as a single piece, problems arose in fabricating the part in an inexpensive manner. The multiple bends that were required were difficult to impart to the piece, and special fixtures or bending jigs had to be devised in order to generate the complex shapes.
Finally, several of the arrangements shown in the prior patents have been found to be expensive to make from the manufacturing standpoint, since it was difficult to assemble the various parts properly. Moreover, with complex mechanisms it has been found to be difficult to realize reliable operation over extended periods of use. Poor reliability was especially troublesome in installations where it was mandatory that the devices operate in their intended manner and with no malfunctioning due to jamming, binding, seizure or breakage of the individual parts.